Afsaneh Akar
- BSc Hons. (Sharif University of Technology, 2017)
Topic
The Study of Ruthenium(II) Half-Sandwich Phosphido Complexes Containing Pentamethylcyclopentadienyl (Cp*) Ligand
Department of Chemistry
Date & location
- Friday, September 6, 2024
- 1:30 P.M.
- Elliott Building, Room 305
Examining Committee
Supervisory Committee
- Dr. Lisa Rosenberg, Department of Chemistry, University of Victoria (Supervisor)
- Dr. David Berg, Department of Chemistry, UVic (Member)
External Examiner
- Dr. Sara Ellison, Department of Physics and Astronomy, UVic
Chair of Oral Examination
- Dr. Roberta Hamme, School of Earth and Ocean Sciences, UVic
Abstract
The catalyst Ru(η5-Cp*)(PPh2H)2(PPh2) was developed by the Rosenberg group for the hydrophosphination of activated alkenes with primary and secondary phosphines. Our group’s recent publication about this system described high activity of this catalyst and preliminary mechanistic studies indicated that the intramolecular proton transfer from the cis-coordinated PPh2H should be the turnover-limiting step for this system.
My work started with further investigating the alkene scope for this system to see the activity and generality of the Cp*Ru catalyst toward a variety of alkenes and to get evidence to support the proposed mechanism for a model hydrophosphination reaction catalyzed by the new catalyst. The activity of the catalyst toward electron-deficient alkenes supported that the mechanism includes the nucleophilic addition of the Ru-PPh2 at the alkene. This investigation also gave evidence that was consistent with the existence of an equilibrium in the proposed mechanism.
I did a kinetic study to obtain the experimental reaction order for substrates involved in the hydrophosphination of methyl methacrylate with PPh2H catalyzed by the Cp*Ru catalyst. The results from this study supported our proposal that the last substitution step is not the turnover-limiting step in this system as it was for the indenyl analogue. Also, an isotope labeling experiment was conducted to get evidence for the proposed turnover-limiting step in the proposed mechanism.
Since the Cp*Ru complexes used to catalyze the hydrophosphination reactions were challenging to isolate due to their high solubility and substitutional lability, they were generated in situ throughout all investigations. The presence of PPh3 ligand in the starting material led to the formation of an orthometallated product during the attempted isolation, so I replaced PPh3 with 1,5-cyclooctadiene (COD) to prevent orthometallation and was able to isolate this complex for R = Ph.